But beautiful diamonds do not need to be intensively dug out of billion-year-old lava pipes. Since 1954, diamonds have been grown inside laboratories in a variety of colors and purities.

For growing gemstones, the most popular method is called chemical vapor deposition (CVD). It starts with a tiny diamond seed which — like all diamond jewelry — is made of a repeating lattice of carbon atoms.

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The seeds are placed inside a microwave plasma oven. The oven zaps natural gas into a plasma of carbon, which sticks to each seed and slowly builds up a diamond, atom by atom.

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A company called Pure Grown Diamonds told Business Insider that it can take anywhere from 10 to 12 weeks to bake up a batch of substantially-sized diamonds in its Singapore lab.

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This is why jewelry-grade synthetic diamonds aren't cheap — and why actor Leonardo DiCaprio and 10 billionaires have invested in Diamond Foundry, which claims it can cut the time to a few weeks.

Any of the company's gems above 1/4 of a carat (a measure of diamond weight) are laser-inscribed with a registry number and graded by their color, cut, clarity, and carat.

The diamonds are then sold to retail outlets as synthetic, sustainable, and conflict-free diamonds.

Outside the jewelry store, you can find cheaper synthetic diamonds everywhere. Like these diamond-encrusted drill bits for powering through glass.

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This diamond — a polycrystalline variety made into a single wafer, made by a company called Element Six— isn't for engagement rings. But the "super material" may be useful in radar systems, communications devices, and perhaps radio telescopes.